design, fabrication and modification of small vtol uav
TRANSCRIPT
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Under the guidance of
Prof. Gp-Capt Praveen Khanna, VSM
On
Design, Fabrication and Modification of Small VTOL UAV
Submitted by:
Akshat Srivastava (07)
Aseem. H . Salim(12)
Shaik Ibrahim (37)
T Shan (38)
Stanley Boswell (40)
Tasdeeq Rahim Sofi (44)
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ACKNOWLEDGEMENT
We would like to take this opportunity to express our hearty thanks to those who helped us in
the course of the Major Project work regarding “Design, fabrication and modification of Vertical
Take-off and Landing (VTOL) Unmanned Aerial vehicle (UAV)”.
First of all, we would like to thank god and our parents for providing moral support needed to
carry out this major project.
We would like to thank our HOD, Dr. Sanjay Singh and Gp Capt. Praveen Khanna,
AMITY INSTITUTE OF AEROSPACE ENGINEERING (AIAE) for allowing us to do our Major
project in this topic.
We would also like to express our sincere gratitude to our Major project guide Prof Gp-Capt.
Praveen Khanna, VSM for his ideas, guidance and support that helped us to fulfill our project work
in time. Without him this project might not have been successful.
Finally, we would like to thank all staffs, aerospace faculty and all those who have directly or
indirectly helped us in completing our internship.
Yours sincerely,
Akshat Srivastava
Aseem H Salim
Shaik Ibrahim Khaleelulla
T Shan
Stanley Boswell
Tasdeeq Rahim Sofi
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ABSTRACT
The target of the project is to design a vertical takeoff Unmanned Aerial Vehicle. The design
configuration selected is a four rotor design. Preliminary calculations regarding the material selection
was performed. Fabrication was carried out beginning with the frame assembly, followed by the
integration of the electronic components. At the same time, the various analyses were performed in
order to predict the real time performance of the Quad rotor design. Beginning with structural
analysis on Catia, the structural deformation of the frame was studied; the analysis was further
refined on the Ansys Workbench. Ansys workbench is an easy to use interactive interface. Following
the structural analysis was the Modal Analysis that was performed to evaluate the resonant
frequencies or the modes of the vibrations of the frame. Then flow simulation was performed again
on the Ansys workbench using the fluent solver and CFX post processing software. This analysis
was performed to study the flow behaviour around the quad rotor design. Various plots of the flow
parameters were obtained and analyzed. After the assembly of all the individual components was
performed, flight testing was performed. The testing was performed for a number of times, various
adjustments were implemented, recalibrated several electronic components. The software was
reconfigured several times to obtain the desired response from the board. The testing has resulted in
minor improvements in the design.
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Table of Contents
ACKNOWLEDGMENT…………………………………………………………………………………………………………………………………..1
ABSTRACT……………………………………………………………………………………………………………………………………………………2
1. INTRODUCTION……………………………………………………………………………………………………………………………………..10
2. HISTORY…………………………………………………………………………………………………………………………………………………13
3. QUADROTOR TECHNOLOGY……………………………………….…………………………………………………………………….......15
4. WORKING OF QUADROTOR……………………………………………………………………………………………………………………16
5. QUADROTOR CONTROL………………………………………………………………………………………………………………………….17
6. HARDWARE CHARACTERISTICS……………………….……………………………………………………………………………………..18
6.1 MECHANICAL COMPONENTS CHARACTERISTICS………………………………………………..……………………19
6.1.1 FRAME CHARACTERISTICS………………….……………………………………………………………………19
6.1.2 PROPELLER CHARACTERISTICS………..………………………………………………………………………..20
6.2 ELECTRICAL AND ELECTRONICS CHARACTERISTICS…………………………………………………………………..21
6.2.1 MOTORS CHARACTERISTICS……………………………………………………………………………………..21
6.2.2 ELECTRONIC SPEED CONTROLLERS CHARACTERISTICS……………………………………………..22
6.2.3 GYROSCOPE CHARACTERISTICS…………………………………………….…..……………………………..23
6.2.4 ACCELEROMETER CHARACTERISTICS………………………………………………………………………..23
6.2.5 TRANSMITTER AND RECIEVER CHARACTERISTICS……………………………………………………..24
6.2.6 MICRO CONTROLLER UNIT CHARACTERISTICS………………………………………………………….24
6.2.7 BATTERY CHARACTERISTICS………………..……………………………………………………………………25
7. SOFTWARE AND CONTROL DESIGN…………………………………………………………………..…………………………………….26
8. STRUCTURES……………………………..……………………………………………………………………………………………………………27
8.1 QUADCOPTER DESIGN……………………………………………………………………………………………………………..27
8.2 COMPARATIVE STUDY……………………………………………………………………………………………………………..28
8.2.1 SCORPID 500 UAV…………………………………………………………………………………………………….28
8.2.2 SIMPLE TILT ROTOR DESIGN……………………………………………………………………………………..29
8.2.3 QUADROTOR DESIGN……………………………………………………………………………………………….30
9. MATERIALS………………………….…………………………………….…………………………………………………………………………..31
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10. CATIA ANALYSIS……………………………………………………………………………………………………………………………………35
11. ANSYS ANALYSIS…………………………………………………………………………………………………………………………………..36
12. AERODYNAMICS……………………………………………………………………………………………………………………………………39
12.1 FORCES ACTING ON QUADCOPTER……………………………………….………………………………………………..39
12.1.1 ROTOR THRUST……………………………..………………………………………………………………….......39
12.1.2 DRAG…………………………………………………………………………………………………………………......42
12.1.3 WEIGHT OF QUADCOPTER…………………………………………………………………………….……….43
12.2 QUADCOPTER MOMENT MECHANISM……………………………………………………………………………………43
12.2.1 TAKE-OFF AND LANDING MOTION………………………………………………………………..………..44
12.2.2 FORWARD AND BACKWARD MOTION………………………………………………………..…………..45
12.2.3 LEFT AND RIGHT MOTION………………………………………………..…………………………………….46
12.2.4 HOVERING POSITION……………………………………………………………………………………………..46
12.3 PERFORMANCE PLOTS……………………………………………………………………………………………………………47
12.3.1 THRUST AS A FUNCTION OF VOLTAGE DROP IN BATTERY……………………………………….47
12.3.2 VELOCITY AS A FUNCTION OF THRUST………………………………..………………………………….47
12.3.3 SLIPSTREAM VELOCITY AS A FUNCTION OF THRUST……………………………………………….48
12.3.4 DISK LOADING AS A FUNCTION OF PROPELLER RADIUS………………………………………….48
12.3.5 ANGULAR VELOCITY AS A FUNCTION OF VOLTAGE DROP……………………………………….49
13. QUADCOPTER DYNAMICS AND MATHEMATICAL MODELLING………………………………..…………………………….50
14. FLOW ANALYSIS IN ANSYS…………………………………………………………………………………………………………………….54
15. SELECTED COMPONENTS SPECIFICATION……………………………………………………………………………………………..58
15.1 SELECTED MECHANICAL COMPONENTS…………………………………………………………………………………58
15.1.1 SELECTED FRAME……………………………………………………………………………………………………58
15.1.2 SELECTED PROPELLERS…………………………………………………………………………………………..58
15.2 SELECTED ELECTRICAL AND ELECTRONIC COMPONENTS……………………………………………………….58
15.2.1 SELECTED MOTORS………………………………………………………………………………………………..59
15.2.2 SELECTED ESCs ………………………………………………………………………………………………………60
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15.2.3 SELECTED TRANSMITTER…………..……………………………………………………………………………60
15.2.4 SELECTED RECIEVER………………………………………………………………………………………………..61
15.2.5 SELECTED MICROCONTROLLER UNIT…………………………..………………………………………….62
15.2.6 SELECTED BATTERY…………………………………………………………………………………………………62
16. HARDWARE SPECIFICATION………………………………………………………………………………………………………………….63
16.1 MECHANICAL…………………………………………………………………………………………………………………………63
16.2 ELECTRICAL……………………………………………………………………………………………………………………………64
17. DESIGN METHODOLOGY………………………………………………………………………………………………………………………66
17.1 FRAME CONSTRUCTION…………………………………………………………………………………………….………….66
17.2 SOLDERING ELECTRONIC COMPONENTS……………………………….………………………………………………67
17.3 FABRICATION…………………………………………………………………………………………………………………………67
17.4 SETTING UP THE KKMULTICOPTER CONTROL BOARD…………………………………………………………….67
17.5 SETTING THE TRANSMITTER………………………………………………………………………………………………….70
17.6 INDIVIDUAL AND COMBINED BINDING OF ESCs…………………………………………………………………….71
17.7 PROGRAMMING AND CALIBRATION OF ESCs…………………………………………………………………………71
17.8 TESTING THE FRAME FOR STABILITY……………………………………………………………………….……………..72
17.9 ADJUSTING GYRO FOR STABILITY……………………………………………………………………………………………72
17.10 PERFORMING FINAL FLIGHT…………………………………………………………………………………………………72
18. INTRODUCTION TO KK MULTICOPTER…………………………………………………………………………………………………..73
18.1 FLIGHT CONFIGURATIONS……………………………………………………………………………………….…………….73
18.2 MOUNTING KKMULTICOPTER ……………………………………………………………………………….………………74
18.3 KKX copter (x Configuration) ……………………………………………………………………………….…………..…...75
19 VIBRATION ANALYSIS……………………………………………………….……………………………………………………………………76
20. VIBRATION ISOLATION………………………………………………………………………………………………………………………....78
20.1 GENERAL CASES……………………………………………………………………………………………………………………..80
20.2 TYPES OF VIBRATION ISOLATION……………………………………………………………………………………………81
21. VIBRATION ISOLATION OF QUADROTOR DESIGN…………….…………………………………………………………….……..85
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22. CATIA DRAWINGS…………………………………………………………………………………………………………………………………86
23. RESULTS……………………………………………………………………………………………………………………………………………….95
24. FUTURE WORKS……………………………………………………………………………………………………………………………………97
25. CONCLUSIONS AND DISCUSSIONS………………………………………………………………………………………………………..99
26. APPENDIX……………………………………………………………………………………………………………………………………………101
27. REFRENCES………………………………………………………………………………………………………………………………………….112
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List of figures
Figure 1: Quadrotor
Figure 2: Oemichen’s Design No:2
Figure 3: Quadrotor concept
Figure 4: System overiew of quadrotor
Figure 5: Basic steps and processes needed in the main code
Figure 6: Scorpid 500 UAV
Figure 7: Simple tilt rotor design
Figure 8: Quad rotor design
Figure 9: Length vs deflection curve
Figure 10: Deflection analysis
Figure 11: Stress analysis
Figure 12: Deflection analysis
Figure13: Maximum principal stresses
Figure 14: Equivalent von-mises stress
Figure 15: Equivalent von-mises strain
Figure 16: Maximum shear stress
Figure 17: The experimental data and the fitted model
Figure 18: The dependence of thrust on rotor speed and wind speed
Figure 19: Pitch direction of Quadcopter
Figure 20: Yaw direction of quadcopter
Figure 21: Roll direction of a quadcopter
Figure 22: Take-off motion
Figure 23: Landing motion
Figure 24: Forward motion
Figure 25: Backward motion
Figure 26: Right motion
Figure 27: Left motion
Figure 28: Thrust as a function of the voltage drop in the battery
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Figure 29: Velocity as a function of thrust
Figure 30: Slipstream velocity as a function of thrust
Figure 31: Disk loading as a function of propeller radius
Figure 32: Angular Velocity as a function of the voltage drop
Figure 33: The inertial and body frames of a quadcopter
Figure 34: Velocity contours
Figure 35: Static prssure contours
Figure 36 : Turbulent Kinetic Energy
Figure 37: Dynamic Pressure
Figure 38: Radial Velocity
Figure39: Velocity Plot
Figure 40: Pressure Plot
Figure 41: Total Pressure plot
Figure 42: Overall frame with everything attached
Figure 43: 10*4.5 inches propellers (clockwise and anticlockwise)
Figure 44: 1800kv brushless outrunner DC motor
Figure 45: 30A Electronic Speed Controller
Figure 46 : FlySky CT6B transmitter
Figure 47 : Receiver FSR6B
Figure 48: KKmulticopter v5.5 control board
Figure 49: 3S 30C 4400mah LiPo battery
Figure 50: Fabrication works done.
Figure 51: kk Multicopter usb connector
Figure 52: kkmulticopter flash tool
Figure 53:T6config software interface
Figure 54: Thrust of lifting force vs Voltage drop of battery
Figure 55: Relationship between peak natural frequency at resonance and loss factor.
Figure 56: Isolation efficiency vs Crossover frequency ratio
Figure 57: Single Degree of Freedom
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Figure 58:Support motion
Figure 59:Passive isolation
Figure 60: Transmissibility vs Frequency
Figure 61:Active isolation control
Figure 62: Transmission vs frequency
Figure 63: Nylon screws
Figure 64: Plastic Pads
Figure 65: Schematic Model of the Design process
Figure 66: Main Frame
Figure 67: Cross Frame
Figure 68: Top Plate
Figure 69: Bottom Plate
Figure 70: Propeller
Figure 71: Motor
Figure 72: Quad copter full view
Figure 73: Design Improvement
Figure 74: Design modeler view
LIST OF TABLES
Table1: Material property calculation table
Table2: Empirical data for 2 blade propellers.
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1. INTRODUCTION
UAVs for military use were reduced to practice in the mid-1990s when the Global Hawk and
the Predator were developed. These were very large fixed wing aircraft with wingspans in the 50 –
100 foot range. Payloads for these large UAVs included radar, laser designators, cameras, and
missile systems. The introduction of these aircraft removed the pilots from harm’s way plus added
the ability to remain in the target area for many hours at a time. These very successful UAVs
represent a fundamental change in the way conflict is managed by the U.S. However, these UAVs
are large and very expensive and they beg the question of whether smaller UAVs could also play a
role in military applications. Likewise, on the other extreme, there is considerable work in micro
UAVs some of which are bio-inspired designs. There are designs modeled after insects and birds, but
just as the large military UAVs are too expensive, we felt that these micro-UAVs were too small to
be practical and required technology that was not readily available to a senior design project group. It
was therefore a vehicle in the one foot to one meter class size that caught our team’s interest and is
the basis for our project. Specifically, our team is very interested in whether these smaller UAVs can
be used not only for military applications but also for commercial and industrial use.
Although most of the large military UAVs are fixed wing aircraft, we felt that a small UAV
should have greater maneuverability and versatility since it was likely to be useful for a broader
range of applications than the larger or smaller versions. We selected the Quadcopter design because
of its maneuverability, stability, and large payload capacity. The UAV that we are building is a
prototype unit that could be used for commercial use but is not rugged or robust enough for military
use. Although we will meet the goal of producing a small UAV that could perform useful missions in
both military and commercial arenas, time and funding constraints forced us to design a UAV to
meet our functional requirements but not to meet harsh environmental conditions such as those
encountered during military missions. However, our UAV design certainly could be re-implemented
with newer and more robust technology which would allow it to be used for military functions.
The Quadcopter configuration UAV will be capable of being remotely controlled to fly
specific pre-determined missions.
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The quadrotor concept was established primarily in an effort to decouple and simplify many
of the issues that currently plague traditional vertical takeoff and landing aircraft. The basic
quadrotor design consists of four complete rotor assemblies attached at equal distances from each
other using booms and a central hub. All the rotors are located within the same plane and oriented
such that the thrust generated by each rotor is perpendicular to the vehicle. If the rotors are
comprised of parts with the same specifications and expected performance, each will produce the
same amount of thrust given a specific power input. The angular momentum of any of the four
rotors generates a torque about the inertial center of mass of the vehicle which can be effectively
counterbalanced by the torque created from the opposing rotor. This configuration requires that
opposite rotors spin in the same direction while adjacent rotors spin in opposite directions. An
immediate advantage to the quadrotor design is that it is not necessary to implement additional
equipment such as control moment gyroscopes with the sole purpose of negating extraneous torques
on the vehicle.
The quadrotor offers many different advantages over other vertical takeoff and landing
vehicles. The single rotor helicopter is notoriously difficult to control and requires blades that are
usually much larger than the vehicle itself. The main hub is extremely complex with multiple
actuating motors and a series of gears to pivot the rotor. Tri-axis control moment gyroscopes are
traditionally implemented to counteract the significant torque produced by the main rotor in addition
to tail blades and ailerons. A quadrotor is able to perform all of the same functions exclusively with
fixed rotors thereby reducing the weight of the aircraft while increasing overall reliability.
Another popular option for vertical takeoff and landing is the coaxial dual rotor aircraft which
relies on the difference in angular momentum between the rotors to maneuver. Although the counter-
rotating blades produce virtually opposing torques, a significant amount of aerodynamic interference
is incurred between the rotors resulting in an inherently less efficient design. Also, it is still
necessary to provide a geared or segmented shaft for the fixed rotors thereby adding some
complexity to the structure. As will be demonstrated later in this report, the quadrotor is not only
optimal in terms of aerodynamic efficiency and structural simplicity but the control algorithms are
much more straight-forward, robust and responsive than the design alternatives.
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Quad rotors are symmetrical vehicles with four equally sized rotors at the end of four equal
length rods. Unlike their counter parts, quad rotors make use of multiple rotors allowing for a greater
amount of thrust and consequently a greater amount of maneuverability. Also, the quad rotors
symmetrical design allows for easier control of the overall stability of the aircraft.
Each of the rotors on the quad-rotor helicopter produces both thrust and torque. Given that
the front and rear motors both rotate counter-clockwise and the other two rotate clockwise, the net
aerodynamic torque will be zero.
2. HISTORY
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Igor Ivanovich Sikorsky once remarked, ―The idea of a vehicle that could lift itself vertically
from the ground … was probably born at the same time that man first dreamed of flying .‖ The first
indicators of this idea can be found in Chinese tops, a toy first used around 400 B.C. Assuming its
inspiration came from the seeds of the sycamore tree, the toy consisted of feathers at the top of a
stick, which was rapidly spun to produce lift and then released into free flight. Although rotorcraft
can trace their roots back thousands of years and often captivated the minds of men like Leonardo Da
Vinci, it wasn‟t until recently that real advances in rotary aircraft were made. Thanks to the work
done by men like Stanley Hiller and Igor Sikorsky, rotary aircraft have become a major part of
modern aviation due to their versatility and ability to take-off and land vertically .
Research into the initial development of quad rotors began in the early twentieth century. One
of the first engineers to attempt to design a quad rotor was Etienne Oemichen. Oemichen began his
research in 1920 with the completion of the Oemichen No.1. This design consisted of four rotors and
a 25 Horsepower motor; however, during tests flights the Oemichen No.1 was unable to obtain flight.
Two years later Oemichen completed his second design; the Oemichen No.2. His second design
consisted of four rotors and eight propellers along with a 125 Horsepower motor. Five of the
propellers were used to achieve stable flight while two were used for propulsion and the final
propeller being used to steer the aircraft. In April of 1914, the Oemichen No.2 achieved an FAI
distance record for helicopters of 360m, which the Oemichen No.2 broke with a distance of 525m.
Figure 2: Oemichen’s Design No:2
While Oemichen had begun working on his early designs in France, Dr. George de Bothezat
and Ivan Jerome began their own research in January 1921 for the United States Army Air Corps.
They completed their design in mid-1922, and the first test flight took place in October of 1922 in
Dayton, Ohio. Bohezat‟s and Jerome‟s design weighed around 1700 kg at the time of take off and
consisted of four six-bladed rotors along with a 220-HP motor. After many tests, the quad rotor was
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only able to achieve a maximum flight time of 1 minute 42 seconds and maximum height of 1.8
meters.
Following the research of Oemichen, Bothezat and Jerome, other researchers have attempted
to create their own successful vertical flying machines. One such was being the Convertawings
Model ―A‖ quad rotor. The Convertawings Model ―A‖ quad rotor was designed and built in the mid
1950‟s with civil and military purposes in mind. This particular quad rotor 5 consisted of four rotors,
two motors as well as wings. Due to lack of interest, however, the Convertawings Model ―A‖ quad
rotor was never mass produced. Currently Bell Helicopter Textron and Boeing Integrated Defense
Systems are doing joint researched on the development of the Bell Boeing Quad Tilt Rotor. The
initial design consists of four 50-foot rotors powered by V-22 engines. The main role of the Bell
Boeing Quad Tilt Rotor will be that of a cargo helicopter with the ability to deliver pallets of supplies
or also deploy paratroopers. The first wind tunnel tests were completed in 2006 and the first
prototype is expected to be built in 2012.
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3. QUADROTOR TECHNOLOGY
Concept exploration
After deciding to create the Quadcopter, we had to decide what electronics to use and which
sensors we would incorporate into it. After a lot of research on the web, we found a couple forums
that discussed open source electronic and software components suitable for making a Quadcopter.
Also, very basic but highly customizable Quadcopter bodies were available that were suitable for us
to use to create our baseline system. The DIYdrones forum provided good information on what was
being done in the amateur drone community and provided important information on what would be
possible for us to use for our project. We believed that the Quadcopter would be a good design
starting point since it could lift off vertically, travel some distance to a specific location, record video
of an object, hover if necessary, and return home upon completion. This scenario led us to the
conclusion that we would need sensors including gyroscope, accelerometer, compass, GPS, and a
battery monitor. We would also need payload components including a camera and a telemetry
system to send imagery back to the liftoff site. Furthermore, we would need a control mechanism
that would allow flight beyond the line of sight since that was also a requirement. We thought of two
approaches for control beyond the line of sight. One was to use the camera and video to allow us to
view the flight path from the Quadcopter point of view while guiding it with an RC controller.
Second, a more ambitious approach would be to use onboard GPS and guidance and a waypoint
system to send commands to the Quadcopter via the telemetry link which the Quadcopter would
execute autonomously. We had no idea if the components we would be able to assemble would meet
the performance requirements. We also had to realistically scope our project given a very small
budget, a small team, and a limited amount of time to complete. We therefore decided to leverage as
many commercial components as possible, get a baseline system working as quickly as possible and
then focus on problems we encountered in the areas of payload design, body design, system
integration, electronics (control board, transmitter, receiver, ESCs and Motor) and mission
evaluation.
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4. WORKING OF QUADROTOR
Each motor applies a torque to its rotor which acts upon the air to produce thrust. There is, of
course, an equal and opposite torque applied to the frame, and so in order to keep the vehicle from
spinning out of control, the torques must be balanced. Torque balance is achieved on the quad rotor
through 2 pairs of counter-rotating blades (on a helicopter, the same balance is achieved using a tail
rotor). If all four motors are applying the same torque, then they exactly cancel each other and the net
effect is a vehicle that is not rotating.
Figure 3: Quadrotor concept
In order change the roll angle of the vehicle (its rotation about the forward-back axis), we can
raise the thrust on left motor and decrease the thrust on the right motor, without affecting the balance
of torques being applied to the vehicle. The same can be done to change the pitch of the vehicle
using the forward and back motors. To cause a change in the yaw angle (direction the front motor is
pointing), front and back motor thrusts are increased while left and right thrusts are decreased, all the
while maintaining the same total thrust and moments.
What makes the quad rotor design attractive, is that four degrees of freedom can be
independently actuated (assuming only small deviations from hover), that is roll, pitch, yaw and
thrust can all be controlled separately, which greatly simplifies control structure of the system.
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Furthermore, this independent actuation is achieved without the need for complicated mechanical
linkages that vary the rotor blade angle (rotor pitch) during each revolution of the blade! This makes
the quad rotor ideal for the RC market as it is clearly easier to build and maintain than a conventional
helicopter design.
5. QUAD ROTOR CONTROL
Dynamic control of a quadrotor is achieved by simultaneously changing the angular velocity
of opposing rotors. For example, forward motion is accomplished by decreasing the angular speed of
rotor 1 while increasing the angular speed of rotor 3 thereby causing a torque imbalance that pitches
the vehicle downward. Positive pitch is achieved by accelerating rotor 1 and decelerating rotor 3 and
results in backward translational motion. Due to symmetry, a roll maneuver can be performed in the
same way as pitch except by employing rotors 2 and 4 instead. In order to remain consistent with the
sign convention of traditional aircraft, positive roll is defined as clockwise rotation about the
horizontal thrust axis.
A yaw maneuver is performed by increasing the angular speed of two opposing rotors while
simultaneously decreasing the angular speed of the other two rotors. If rotors 1 and 3 accelerate and
rotors 2 and 4 decelerate, the vehicle will undergo yaw in a counterclockwise direction. Vertical
translation is achieved by simultaneously increasing the angular speed of all four rotors to the point
where the total thrust generated exceeds the weight of the vehicle. As expected, the quadrotor will
hover if the total thrust generated is exactly equal to the weight of the quad rotor.
It has been demonstrated that a vertical takeoff and landing vehicle should be able to create at
least 25% more thrust at maximum power than the weight of the vehicle in order to safely and
efficiently maneuver.
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6. HARDWARE CHARACTERISTICS
Block Diagram
The best way to start the design phase is by drawing a block diagram, which does a great job
explaining the whole system layout in short. The block diagram in figure demonstrates the main
components of the Quadrotor, in addition it also clarifies how each component is interfaced and
coupled with the other parts.
Figure 4: System overview of the quadcopter
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6.1 Mechanical Components Characteristics
In this section, the desired characteristics of the mechanical components will be discussed.
Mainly what are the characteristics and features that have been considered while designing the
Quadrotor. Of course also some technical aspects will be mentioned.
6.1.1 Frame characteristics
The most suitable way is to begin with is the skeleton of the Quadrotor, the frame. The frame
is considered the largest (in volume) component used in the Quadrotor and a very important one.
Choosing a frame to fulfill the required need is essential, critical, and also not simple. The frame
should be light-weight yet strong to tolerate possible accidents and crashes, it has also to be thin.
Light: A feature that is quite important in aircraft and vehicles, and in Quadrotors it is no
exception. Ultimately the goal is to reach the best possible flight time, and to do so the weight
of the frame should be minimal. This also would assure a better stability and controllability of
the Quadrotor.
Strength: Having a frame that is sturdy and strong is vital, as the Quadrotor could crash, or
have an accident due to a wrong landing.
Thin: It is quite critical to have a frame that is thin due to several issues; since the Quadrotor
has four motors spinning at a very high speed, consequently during the flight those motors
will eventually get very hot (depending on flight conditions). Hence, having a proper air
flow is a must to cool down the inner components of the motors and prevent any damage due
to overheating. Another upside of a thin frame is that the vertical air flow generated by the
propellers won't be hindered by a wide frame, contributing in a better flight stability.
Another issue that should be discussed about the frame is its length. The focus in this case is
the distance between the middle points of each opposite motor. It's preferred to cut down this
distance as much as possible due to several reasons; it's a good way to make the power needed from
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each motor to stabilize and/or fly the Quadrotor around. Another good side is that it would enhance
the controllability, maneuverability, and also contribute in reducing the overall frame weight.
Now since the design of the Quadrotor would be an x-shaped, at the center of the shape
should exist a plate (bed) where the on-board controller would rest on it and then covered to ensure
protection of anything resting there, from cables to the controller itself. This plate should also be
sturdy and at the same time light-weight.
To ensure safety and avoid severe damage of the Quadrotor, it has been a priority to also
design some safety features. First off a proper landing gear is important to be installed. In case of a
faulty landing or an error during flight time, the landing gear should be able, or at least, minimize the
damage and impact on the whole Quadrotor. A flexible landing gear would be a good way to assure
this.
Next is the fact that the exposed propellers are absolutely dangerous for the Quadrotor itself
and the humans around it. Those propellers are, as said before, spinning at very high speeds during
flight and would certainly and seriously hurt someone badly if something went wrong. The damage
could affect the Quadrotor itself, say the Quadrotor hit a wall, an object, or an obstacle, the
propellers would break and be shattered. The motors could take damage and become unusable. Plus
also the shattered pieces could hurt anyone around them. Such reasons are quite persuasive to
consider designing protection around the propellers, at least during flight time and the testing phase.
And could be removed when the Quadrotor is ready and reliable.
6.1.2 Propellers Characteristics
The mechanical lifting elements of the Quadrotor are the propellers. They do come in
different sizes, shapes, and materials; which makes the decision somehow flexible in choosing one.
High quality propellers are made by different manufacturers to deliver great performance of lifting
power at a very small weight; to minimize the torque needed for spinning them by the motor's rotor.
As mentioned propellers are manufactured from a variety of materials such as; plastic, which is
cheap, available, and light, but is by nature fragile meaning it could be damaged or broken easily.
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Wood is another example, it is tough and mid-priced but is certainly heavier than plastic. Lastly is
the carbon fiber which is tough and light-weight but more expensive than the previous two types.
Choosing a suitable size is quite crucial in the design of the Quadrotor, since it affects the
power consumption, the overall weight, and how sturdy and reliable (stable-wise) the Quadrotor is.
Increasing the size of the propellers means higher thrust delivered, but that comes at the cost of more
torque required to spin them by the motors. Having that in mind, the criterion for choosing the
propellers is mainly dependent on the model that is being built and its overall weight. As the goal
states, the Quadrotor should be about 3 kg and propellers with the size 10*4.5 inches are appropriate.
Importantly is the fact that four propellers are needed, but with a pair being oriented for
clockwise (CW) direction and the other pair for the the counter-clockwise (CCW) direction.
6.2 Electrical & Electronic Characteristics
The design of electrical and electronic components is absolutely an exhausting phase, picking
components and parts that will cooperate and be interfaced together to make the Quadrotor
successful was filled with hardships. As each of these components would be synchronized and
affected by the others, in addition to the fact that each component is a main player in the design
process, care and precision are a must. In this section a thorough discussion about this phase will be
mentioned.
6.2.1 Motors Characteristics
The motors are no doubt one of the most important elements in the Quadrotor; they are the
―muscles‖ of it. With that in mind it's quite important to choose the right motors to do the job, as the
impact of those is huge on how satisfying and good the final outcome is. Brushless DC (BLDC)
motors have several advantages over brushed motors and are a superior choice; due to the lack of
mechanical parts and the absence of brushes, as mentioned before, the BLDC motors are more
efficient (converting electrical to mechanical energy) than brushed DC motors since there are no
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friction losses due to the brushes. The BLDC motors are also less subjected to service and
maintenance, again because of no friction, the mechanical wear is eliminated which guarantees a
longer life-time and better reliability. Less noise generated when operating and since the motor
would be covered in a housing, any cooling issues are almost solved. A BLDC motor's only
disadvantage is its high cost in comparison with a brushed DC motor, as it would require a
sophisticated electronic speed controller (ESC) to run it and control its speed. Also the
manufacturing of a BLDC motor isn't as simple as the brushed DC motor. On the long run though,
the cost of a BLDC is theoretically lower keeping in mind that it has a longer life-time than a
brushed one which would compensate its higher cost. For the Quadrotor, choosing a BLDC motor is
definitely a righteous call, but that's not everything. Since the Quadrotor is a remote-controlled (RC)
propelled aircraft project, a specific type of a BLDC motor called outrunner (the outer shell spins
around the windings) is very suitable to operate the Quadrotor with ease due to several factors;
despite the fact that this type is slower than inrunners BLDC motors (the rotational core is housed in
the motor's can) but that means that the torque produced is much higher, this exactly is the selling
point why outrunners are a perfect choice to run the propellers. It's also quite efficient from a weight
point of view, because there is no need for a gearbox, ridding the Quadrotor from it's complexity,
noise, inefficiency, and extra weight.
6.2.2 Electronic Speed Controller (ESC) Characteristics
ECS's are required to run the BLDC motors in the Quadrotor. The ESC is a standalone chip
that's connected to the receiver's control channels and then coupled with the BLDC motor. For a
better understanding of the ESC, it's more conventional to consider it as a pulse-width modulation
(PWM) controller for the BLDC motors. PWM in short is a great way of controlling some modern
electronics such as a BLDC motor, a fast variation between the motor being fully off and fully on
powered, more conveniently described as a percentage called the duty cycle. Controlling the duty
cycle means controlling the speed of the BLDC motor without any losses and also without affecting
the load.
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6.2.3 Gyroscope Characteristics
At the beginning of the project, the aim was to achieve a self-stabilized Quadrotor, in order to
achieve that there has to be a kind of feedback, that tells the microcontroller that the Quadrotor is
tilting or leaning. This special feedback is achieved through a gyroscope. A gyroscope is a sensor
that measures the angular rate or velocity (speed of rotation). When rotating it also gives a positive or
negative readings, and while stationary gives a constant value.
Choosing an appropriate gyroscope is dependent on a number of factors; the gyroscope
should be fast and responsive, in other words it should be able to detect minimal changes in the
angular velocity in order to compensate the errors faster which would guarantee the prevention of the
accumulation of errors. It should also be small, and light-weight, usually Micro Electro-Mechanical
Systems (MEMS) manufactured sensors do a great job featuring these two aspects. And because of
the existence of noise, a built-in filter is also a plus, in addition to a conditioning circuit embedded on
the chip that would help a lot in cutting extra parts and complexities.
Since the Quadrotor is governed by three degrees of freedom (pitch, roll, and yaw), a 3-axis
gyroscope is needed.
6.2.4 Accelerometer Characteristics
An accelerometer is a sensor capable of measuring the amount of acceleration, also could
measure the tilt. Implementing the accelerometer and the 3-axis gyroscope together on a single chip
yield the inertial measurement unit (IMU). This unit utilizes both sensors to do an outstanding job in
keeping the Quadrotor as much stable and level as possible, plus having two sensors on one chip
reduces any extra space needed.
Knowing that the implementation (from a code point of view) isn't anything but hard and
complex, nevertheless utilizing some of the true potential of the accelerometer would affect the final
outcome and results. A 3-axis accelerometer would seem to do that job.
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6.2.5 Transmitter & Receiver Characteristics
For the pilot to command the Quadrotor from the ground, a transmitter or a remote-control
(RC) is needed. This should have a good range and both a pre-programmed and user-programmed
channel mixing for a better flexibility and usage. The number of channels is also an aspect that
should not be left out, having a proper amount of channels is always a plus, as it would greatly
enhance the features and tweaks that could be utilized and later on added to the Quadrotor.
The receiver, which is used to get the commands sent from the transmitter by the pilot, would
be directly coupled with the microcontroller through the PWM I/O pins. Having a receiver with
channel and frequency selection seems suitable, offering a user-friendly solution.
6.2.6 Microcontroller Unit (MCU) Characteristics
The on-board controller is without a doubt a vital component in the Quadrotor. The fact that
the on-board controller will be the one responsible for dispatching a variety of instructions to the
other components, yet also receive certain commands from the pilot and the feedback coming from
the sensors. A proper microcontroller would accomplish such tasks if properly selected. Definitely a
microcontroller is the way to go, because of its capabilities despite its weight and size.
With that in mind, the selection of a proper microcontroller is critical and should be based on
a specific criterion, summarized as follows:
Speed of operation; in other words how fast and agile is the processing power? Having a
suitable computational power in the Quadrotor is a must, because during flight time, the
controller should be very responsive and quick to guarantee a stable and a well-behaving
flight.
Cost; both the hardware and the software to run it. Sometimes the cost of these could and
will eventually mean the need to compromise.
Power needed to run it; yet another reason to maximize the flight time, the power
consumption of the controller should be as minimal as possible.
Data storage; i.e. memory. The controller should provide enough memory to handle the
program and code embedded. A project could fail because of the lack of memory.
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Number of I/O ports; when designing the system, one should possess the knowledge of how
many inputs and outputs are needed. Selecting a controller that shorts in input or output ports
could cause unneeded troubles.
Analog capabilities; some controllers lack these such as; ADC, DAC, or a comparator. In
such case this would require to have extra few components and undesired clutter.
Serial communication; which communication protocol is used to interface the
microcontroller? USB would be a great solution, since it's an industry standard and readily
available.
Development tools; extra tools and programs that might be needed to fully utilize the
microcontroller. Again it could be a cost point of view, or its availability.
Environmental conditions; where would it be mounted? Temperature and humidity issues
should also be considered.
With the help of these guidelines, the selection of the microcontroller is clearer and more
convenient. Importantly in the case of the Quadrotor that the microcontroller selected should be
powerful, light-weight, easy to interface with a computer and prototype which, has enough I/O ports,
and easy on the pocket.
6.2.7 Battery Characteristics
Having four motors in a Quadrotor that produce high thrust power, that means high current
consumption is required. So a battery with high current capacity and discharging rate is needed. Such
batteries are available in the market but with much larger scale and weight than normal batteries, and
minimizing the weight of components on a Quadrotor is a very crucial matter to consider so that an
efficient stable flying system can be achieved. Also it shouldn't be missed that the wires used in the
connections between motors, ESC's, and batteries are able to withstand high current discharge.
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7. Software & Control Design
After selecting the right hardware components, the next step is to have a proper design for the
code that will run on the Quadrotor. This phase is the hardest of all and needs so much patience and
constant tuning and monitoring. Having a snappy control loop is essential as the Quadrotor tries to
self-stabilize itself, without such a loop, the flight could be sluggish with a huge amount of errors,
which will be also accumulative and eventually would result in a crash with unexpected
consequences. Starting off with a simple, yet very enriched flow chart of how should the program
embedded in the microntroller look like and behave. A flow chart is very similar to the block
diagram; brief and comprehensive. In figure, the flow chart shows the basic steps and processes
needed in the main code.
Figure 5 : basic steps and processes needed in the main code
To summarize the flow chart, it begins with providing the power through the battery, at this
instance hardware components will initialize and boot. After that the sensors will be calibrated,
taking the nominal value that they ―see‖ and consider it as the reference. The receiver would then
start testing the frequency and channels in order to make sure that it is correctly connected with the
transmitter. The phase called arming can now take place, setting different modes and configuration
such as; turning the whole system off (disarm). The next two steps are mainly getting the values that
the sensors read and then sending those values to the proportional-Integral (PD) which will get the
error and provide the final values with the help of the desired values from the transmitter and
receiver. To conclude, mixing is the process of sending the commands to the motors based on the
desired input plus the output value generated from the PD.
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8. STRUCTURES
The section of weights and structures was set with following objectives:
Designing the overall structure of the quadcopter and keeping track of the actual and
estimated weights.
The overall placement and layout of components.
The stress and deflection analysis.
In order to achieve these members analyzed various building materials, also the tables of
actual and estimated weights were kept and updated as the various designs progressed.
8.1 QUADCOPTER DESIGN
To meet the mission objective of quadcopter design the following goals were set:
The square cross section bars should not have length greater than 72 cm.
The two plates i.e., the upper and the lower plate are of same length = 21 cm.
Overall weight which includes the weight of all individual components of quadcopter should
be less than 4 kg.
The most light and strong material should be used for the construction of the quadcopter , the
team decided that ALMUNIUM should be used as it was light, cheap and readily available in
market.
To maximize the stability, it was decided to design the quadrotor in such a way as to keep the
center of gravity as low as possible.
Finally the goal of keeping the quadcopter design relatively simple to construct and repair
was set. This final goal was set so that as much time as possible could be devoted to testing
and improving the vehicle, rather than assembling and fixing it.
In the beginning design stages, several comparable quadcopter designs were researched and
analyzed. The four influential designs which were researched and analysed , with their comparative
study are given below :
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8.2 COMPAPITIVE STUDY
8.2.1 Scorpid 500 UAV
The SCORPID-500 is now fully stabilized and controlled by a 9 DOF IMU (ArduIMU+ v2,
HMC5843, GPS with firmware TriStab v3.3 JLN). The SCORPID-500 VTOL UAV uses an
innovative design based on Gary Gress concept from Gress Aero. The Oblique Active Tilting (OAT)
at 45° of the twin engines allows a full pitch control by using the induced gyroscopic moment.
Today, the SCORPID-500 UAV prototype has done its first successful flights full IMU stabilized. Its
flight is very stable. The earlier prototype has used 4 gyroscopes on board and some additional
mixers.
Figure 6: Scorpid 500 UAV
Advantages
Oblique Active Tilting from Gary Gress concept provides a great deal of self-stability to
UAV.
Relatively simple frame design.
No servos required as the motors are self-tilting in nature.
The Yaw is controlled with a differential tilt of the motor.
The Roll is simply controlled with a differential speed of the motor.
The Pitch uses the OAT concept. The spinning propellers acts as spinning gyroscope, when
they are tilted on a horizontal axis set at 45° from the pitch axis, their gyroscopic moment
induces a torque on the pitch axis. This is a true active control with a called CMG (Control
Moment Gyroscope).
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Disadvantages
The OAT flight model is complex and the PIDs tuning is a big challenge.
Self-axis tilting rotor is costly and requires large current and esc’s with greater capacity
Complex control board is required for the ensuring the stability and good quality control
board has a greater cost.
Time constraints restrict the complete conceptual design and fabrication of this particular
model.
8.2.2 Simple tilt rotor design
Figure 7: Simple tilt rotor design
Advantages
Very simple Design consisting of a wooden frame with the rotors mounted at the two ends.
The motors are mounted on a frame that can be tilted about the axis through the servos and
tilting mechanisms. Entire controls are enclosed within a simple rectangular box.
Very light in weight because of the wooden frame used, so lesser power battery and lower
specifications motors and esc’s can be used.
The control board and the remote controls are relatively inexpensive.
Disadvantages
Though very simple in design, it faces a serious problem in its stability. The pitching motion
renders instability because of the cg movement.
The mechanisms needed for tilting the rotors requires 3 servos for tilting the rotors for
achieving all the desired motions in addition to the esc’s and motors.
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Greater number of electronic components created a difficulty in channelizing the controls to
the remote control. Greater channels required.
Inherently unstable in nature.
8.2.3 Quad rotor design
A quad copter is a multicopter that is lifted and propelled by four rotors. Quad rotors are
classified as rotorcraft, as opposed to fixed-wing aircraft, because their lift is generated by a set of
revolving narrow-chord airfoils. Unlike most helicopters, quad rotors generally use symmetrically
pitched blades; these can be adjusted as a group, a property known as 'collective', but not
individually based upon the blade's position in the rotor disc, which is called 'cyclic'. Control of
vehicle motion is achieved by altering the pitch and/or rotation rate of one or more rotor discs,
thereby changing its torque load and thrust/lift characteristics.
Figure 8: Quad rotor design
Advantages
Relatively smaller blades
Structure is stable and each rotor has to support only a 25% of the total weight.
Ease of design of the frame and less complexity in the controls attachment.
All the motions are independent viz. Pitch, Roll and Yaw as compared to the fixed wing
where the roll and the yaw motions are couple.
The quadcopter because of its relatively simple and stable configuration was chosen as the final
design.
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9. MATERIALS
An important factor in the design of the quadrotor was the materials used Three primary
factors were considered when choosing the materials: strength, deflection and weight. Using these
criteria, several different materials were studied and compared, including cast Aluminum , balsa
wood class IV, birch wood class IV, PVC (hard), nylon, carbon fiber, and basswood.
The primary focus was laid on the bars, as these were the members which would experience
the highest forces and moment out of all the parts in the quadcopter. To analyze the various
materials, the following parameters were calculated for each material:
Bending stress (σ) = M.y/ Ixx.
Factor of safety (FS) = tensile strength / σbending
Deflection formula (δ) = FL3 / 3EIx.
Weight = ρ * volume
where :
M = moment
ρ = density
Y = moment arm
Ixx = moment of inertia about x-axis
F = force
L= length of bar
E = young’s modulus of material
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Figure 9: LENGTH VS DEFLECTION CURVE
From above graph we can see that carbon fiber has the minimum deflection for any given
length of the beam but as carbon fiber was not easily available in the market so we choose Al as it is
having next minimum deflection for any given length and also it was easily available in market.
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Table1: Material property calculation table
PARAMETERS ALUMINUM
BALSAWOOD
CLASS IV
BIRCHWOOD
CLASS IV
PVC
HARD
BASS
WOOD
CARBON
FIBRE
NYLON
DENSITY
Kg/ m^3
1591.44 130 610 1500 398 1490 1140
Youngs
modulus(E)Gpa
70.0 6 16.5 4.140 10.091 631.00 2.61
Tesile strength
Gpa
0.150 0.075 0.270 0.062 0.060 1.379 0.083
Deflection(cm) 0.33 3.95 1.44 5.7 2.35 0.037 9.09
**Length of bar for each material was taken as 70 cm and tip load was 26.9794 N.
Table: displays the material properties and calculated deflections for the various materials that were
being considered. From this information, it was calculated that Balsawood Class IV would actually
be the lightest material to construct the bars but it is not having sufficient strength.
Also carbon fiber was having the highest weight to strength ratio but Aluminum was chosen because
it was easily available in market and it has excellent strength-to-weight ratio, desirable thermal
characteristics and is easy in precise machining.
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The overall placement and layout of components
The quadcopter consists of 4 booms and central hub. The central hub of the vehicle consists
of two square aluminum plates. Booms are made of hollow square cross-section Aluminium bar.
Each boom holds speed controller and brushless DC out runner motor. The lower plate holds the
batteries. The two plates are held together by four booms which also serve as the attachment point
for the rotor arms. All the bars on the vehicle are made of hollow 20mm square cross-section
Almunium. Each of the motors is mounted on the end of each boom ( 3cm inside from tip).The
battery is attached to the lower plate at the center of the two plates. The control board is located on
the upper plate at the center of the two plates.
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STRESS AND DEFLECTION ANALYSIS
For stress and deflection analysis we used two well-known softwares. In the early stage of
our design we performed the analysis on CATIA so as to get a rough idea about the structures that
we are going to use in our design, a much better and refined analysis was done on ANSYS in latter
part of our project.
10. CATIA ANALYSIS
DEFLECTION ANALYSIS (Fig: 10)
STRESS ANALYSIS (Fig: 11)
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11. ANSYS ANALYSIS
DEFLECION ANALYSIS (Fig: 12)
MAXIMUM PRINCIPAL STRESSES (Fig: 13)
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EQUIVALENT VON-MISES STRESS (Fig: 14)
EQUIVALENT VON-MISES STRAIN (Fig: 15)
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MAXIMUM SHEAR STRESS (Fig: 16)
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12. AERODYNAMICS
The Aerodynamics of quadcopter is divided in following subtopics :
Forces acting on quadcopter.
Quadcopter moment mechanism.
Performance plots.
Quadcopter dynamics and its mathematical model.
Flow analysis.
12.1 Forces acting on quadcopter
The various forces acting on quadcopter are:
Rotor thrust.
Drag.
Weight of quadcopter.
12.1.1 Rotor thrust
The thrust produced by a rotor in flight is in general a function of the relative velocity
between the rotor and the surrounding air, V, as well as the angle of attack α . For the situation where
α=π/2, the craft is said to be in climb. The velocity of the slipstream increases as it passes through the
rotor. We refer to this additional velocity imparted by the rotor as the induced velocity, (υ).
Momentum theory analysis relates the additional kinetic energy of the air at an infinite distance from
the rotor to the thrust, and provides us with an expression for the thrust in climb or descent.
Here T is the rotor thrust, ρ is the density of air, A is the area swept by the rotor, m is the
mass flow through a disc of area A and w is the velocity of the air an infinite distance after it has
passed through the rotor. In order to have a complete system of equations, we turn to blade element
theory to find another expression for the thrust in climb from a rotor.
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Here ω is the rotor speed, R is the radius of the rotor, ᶱtip is the pitch angle at the blade tip, a
is the lift curve slope, b is the number of blades on the rotor, and c is the blade chord. a, b, c, and
ϴtip are functions of the rotor geometry alone. Note that if V is 0, the induced velocity is equal to
(T/2ρA)0.5
.Given (8) and (9), a climb velocity V and angular speed w we can solve a quadratic
equation for n and then use either expression to find the thrust. In (9) we have two groups of terms
describing the geometry of the rotor which depend on assumptions about the rotor construction, e.g.,
that it is ideally twisted and has a constant chord. By grouping the terms we can rewrite (9) as
where k1 and k2 are determined by the rotor geometry and the density of air. One approach
for finding these constants would be to measure the physical parameters of the propeller; however,
this approach suffers from reliance on many assumptions about the blade geometry. Instead we
choose to empirically determine these constants. We collect test rig and in-flight data to find the
constants which best describe the experimental data. The in-flight test was performed by
commanding a micro quadrotor to ascend or descend at a constant velocity. We then measured the
steady state rotor speed to determine w required to produce a thrust of mg at the given vertical
velocity. Several data points were collected for each velocity by adding small amounts of weight to
the quadrotor to vary the required thrust.
The maximum error between the fit and the experimental data is .64 g over all trials.
Figure 17: The experimental data and the fitted model
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Experimental Data and Fitted Model for Thrust as a Function of Air and Rotor Speed Once
we have constants k1 and k2, we can predict the thrust at a given V and ω using our model following
a two-step process:
First, solve for n by finding the roots of the quadratic equation formed from above equations.
Choose the positive root as the reasonable physical induced velocity.
Substitute n into 3rd
equation to find the predicted thrust.
We can implement this procedure in reverse to find the ω which produces a given thrust at
the current vertical velocity. In forward flight, we must add angle of attack α to our model as shown
in Figure. The equations for thrust become:
where ϴ is the pitch angle and is a function of rotor geometry alone as we are considering
fixed pitch rotors . The equation for υ is now a fourth order polynomial instead of a quadratic. We
characterized the dependence of thrust on rotor speed using the thrust test rig for five angles of attack
and four wind speeds at each angle. The total thrust produced by the rotor decreases notably with
increased wind speed in a given direction. As the angle of attack increases, the thrust variation due to
wind speed decreases, as the component of wind velocity perpendicular to the rotor increases more
slowly. At α= 30, the effect of wind speed has decreased significantly, such that the largest observed
difference between the no wind condition and the highest wind speed condition is 1 g.
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Figure 18: The dependence of thrust on rotor speed and wind speed
With the help of momentum theory we have calculated the following parameters:
Thrust at each propeller = 2.753 kg = 26.9794 N
Total thrust developed = 107.91 N
Velocity across the disc = 14.745 m/s
Velocity after the disc = 29.49
Power produced due to each rotor = 397.81 w
Power loading = 0.0678
Disc loading = 532.71 N/m2
Inflow parameter = 0.3870
Thrust coefficient = 0.2995
Power coefficient = 0.1159
12.1.2 Drag
The drag includes the induced drag , the interference drag ,pressure drag, skin friction drag
and the total drag sums to =
Note that drag calculation is not a primary consideration in UAV design so much emphasis is
not laid on drag calculation and drag reduction.
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12.1.3 Weight of quadcopter
The force on quadcopter is due to the weight of the quadcopter. The weight of quadcopter
consists of its individual components which include the battery, plates, beams and other electronic
components.
12.2 Quadcopter moment mechanism
Quadcopter can described as a small vehicle with four propellers attached to rotor located at
the cross frame. This aim for fixed pitch rotors are use to control the vehicle motion. The speeds of
these four rotors are independent. By independent, pitch, roll and yaw attitude of the vehicle can be
control easily. Pitch, yaw and roll attitude off quadcopter are shown below.
Figure 19: Pitch direction of Quadcopter
Figure 20: Yaw direction of quadcopter
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Figure 21: Roll direction of a quadcopter
12.2.1 Take-off and landing motion mechanism
Take-off is movement of Quadcopter that lift up from ground to hover position and landing
position is versa of take-off position. Take-off (landing) motion is control by increasing (decreasing)
speed of four rotors simultaneously which means changing the vertical motion.
Figure illustrated the take-off and landing motion of Quadcopter respectively.
Figure 22: Take-off motion
Figure 23: Landing motion
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12.2.2 Forward and backward motion
Forward (backward) motion is control by increasing (decreasing) speed of rear (front) rotor.
Decreasing (increasing) rear (front) rotor speed simultaneously will affect the pitch angle of the
Quadcopter.
Figure 24: Forward motion
Figure 25: Backward motion
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12.2.3 Left and right motion
For left and right motion, it can control by changing the yaw angle of Quadcopter. Yaw angle
can control by increasing (decreasing) counter-clockwise rotors speed while decreasing (increasing)
clockwise rotor speed. Figure 3.9 and 3.10 show the right and left motion of Quadcopter
Figure 26: Right motion
Figure 27: Left motion
12.2.4 Hovering or static position
The hovering or static position of Quadcopter is done by two pairs of rotors are rotating in clockwise
and counter-clockwise respectively with same speed. By two rotors rotating in clockwise and
counter-clockwise position, the total sum of reaction torque is zero.
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12.3 PERFORMANCE PLOTS:
12.3.1 Thrust as a function of the voltage drop in the battery (Figure 28)
The thrust generated by the propeller depends on the rpm of the rotating disc. The rpm, in
turn, depends on the voltage and the current drawn by the motor from the battery. The battery
voltage can fluctuate between 7 to 11.1 volts, since it is a 3 cell battery. So, when the voltage drops,
the rpm and in turn the lifting force generated by the propellers also drops.
12.3.2 Velocity as a function of thrust (Figure 29)
In the above curves, we can see that since the thrust developed by the propellers drops, so, the
velocity across the rotor disc also decreases in the similar way.
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12.3.3 Slipstream velocity as a function of thrust (Figure 30)
Slipstream velocity is the velocity of the flow at a certain small distance away from the
rotating disc. Since, the slipstream velocity is twice the velocity across the disc, hence, as the
velocity across the disc decreases, the slipstream velocity decreases.
12.3.4 Disk loading as a function of propeller radius (Figure 31)
Disk Loading is the ratio of the Thrust developed to the disk area. Since, the disk loading is
inversely proportional to the disc area, so as the propeller radius increases, then the disk loading
decreases.
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12.3.5 Angular Velocity as a function of the voltage drop (Figure 32)
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13. Quadcopter dynamics and mathematical Modelling
To understand how to control the helicopter, we must first understand how it behaves. The
derivation of the equations of motion is built of the Lagrangian equations of motion for both
translational and rotational kinetic energy, and potential energy. The energy equation for a quad rotor
has three terms, the translational kinetic energy, the rotational kinetic energy, and the gravitational
potential energy.
The quadcopter structure is presented in figure including the corresponding angular
velocities, torques and forces created by the four rotors (numbered from 1 to 4).
Figure 33: The inertial and body frames of a quadcopter
The absolute linear position of the quadcopter is defined in the inertial frame x, y, z axes with
ζ. The attitude, i.e. the angular position, is defined in the inertial frame with three Euler angles η.
Pitch angle (ϴ) determines the rotation of the quadcopter around the y-axis. Roll angle (ᶲ)
determines the rotation around the x-axis and yaw angle (ψ) around the z-axis. Vector q contains the
linear and angular position vectors
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The origin of the body frame is in the center of mass of the quadcopter. In the body frame,
the linear velocities are determined by VB and the angular velocities by υ
The rotation matrix from the body frame to the inertial frame is:
in which Sx = sin(x) and Cx = cos(x). The rotation matrix R is orthogonal thusR−1
= RT which is the
rotation matrix from the inertial frame to the body frame.
The transformation matrix for angular velocities from the inertial frame to the body frame is
Wη, and from the body frame to the inertial frame is Wη−1
Where Tx = tan(x). The matrix Wη is invertible if (ϴ) not equal to (2k − 1) ᶲ/2. The
quadcopter is assumed to have symmetric structure with the four arms aligned with the body x-and y-
axes. Thus, the inertia matrix is diagonal matrix I in which I xx = Iyy.
The angular velocity of rotor i, denoted with ωi creates force fi in the direction of the rotor
axis. The angular velocity and acceleration of the rotor also create torque around the rotor axis
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Lift constant is k, the drag constant is b and the inertia moment of the rotor is IM.
The combined forces of rotors create thrust T in the direction of the body z-axis. Torque B
consists of the torques τɸ, τɵ and τψ in the direction of the corresponding body frame angles.
In which L is the distance between the rotor and the center of mass of the quadcopter. Thus,
the roll movement is acquired by decreasing the 2nd rotor velocity and increasing the 4th rotor
velocity. Similarly, the pitch movement is acquired by decreasing the 1st rotor velocity and
increasing the 3th rotor velocity. Yaw movement is acquired by increasing the angular velocities of
two opposite rotors and decreasing the velocities of the other two.
Translational forces on the quad rotor are given by the equation
In this equation R is the direction cosine transformation matrix, given by:
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From above equation we then determine the non-linear equations of motion:
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14. FLOW ANALYSIS IN ANSYS
Flow analysis over a propeller blade
1. Velocity contours (Figure 34)
2. Static prssure contours (Figure 35)
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3. Turbulent Kinetic Energy (Figure 36)
4. Dynamic Pressure (Figure 37)
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5. Radial Velocity (Figure 38)
Velocity Plot (Figure 39)
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Pressure Plot (Figure 39)
Total Pressure plot (Figure 40)
Drag Forces on the propeller
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15. SELECTED COMPONENTS SPECIFICATIONS
15.1 Selected Mechanical Components
15.1.1 Selected Frame
The frame used in the Quadrotor is custom made. It consists of four aluminum hollow square
cross-section drilled bars and two square center plates (Top and bottom) made of Aluminium. The
frame weighs about 400 g, depending also on the type and number of screws used. The distance
between the centers of two aligned motors is 64cm. To mount the microcontroller over the top plate,
we have used nylon screws. Battery is mounted on lower plate and ESC and motor on each boom.
Figure 41: Overall frame with everything attached
15.1.2 Selected Propellers
As for the propellers used, they are the EPP1045, 10*4.5in propellers for right and left rotating.
Figure 42: 10*4.5 inches propellers (clockwise and anticlockwise)
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15.2 Selected Electrical & Electronic Components
15.2.1 Selected Motors
The motors selected to actuate the Quadrotor are the BLDC outrunners type EK5-0003B.
Weighing each 62 g, these small motors are capable of 1800 rpm/Volt, maximum efficiency of 80%,
and a maximum current of 16A. Each motor can produce a maximum thrust up to 2kg. The motor is
illustrated in figure.
Figure 43: 1800kv brushless outrunner DC motor
Considering the 2:1 ratio between motors thrust power to Quadrotor's weight is important.
Having a light-weight Quadrotor and relatively strong motors implies the fact that the control of it
would be harder since the overrated power of the motors ratio to the Quadrotor weight would easily
produce an unstable flight, and therefore the control algorithm has to be accurate. No compromise.
The amount of rpm/Volt is mainly dependent on the Quadrotor's weight and size, as for bigger sizes
low rpm/Volt is better (higher torque) and for small sizes the opposite.
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15.2.2 Selected Electronic Speed Control (ESC)
The required ESC needed to run the motor is 25 A, our ESC’s are capable to deliver constant
current up to 30 and burst current 40A, which is quite enough and safe. Weighing about 25 g and
with a lot of features such as; superior current endurance, protection features, different operating
modes depending on the aerial platform used, and a throttle range that can be programmed and
compatible with all transmitters available in the market. Figure shows the ESC picked.
Figure 44: 30A Electronic Speed Controller
15.2.3 Selected Transmitter
The transmitter used in the Quadrotor is FLY SKY CT6B. Having 6 channels and user-
defined channel mixing makes it a suitable choice.
Figure 45: FlySky CT6B transmitter
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15.2.4 Selected Receiver
As for the receiver, the FlySkyR6B is selected. The receiver receives the signal from
transmitter at a frequency of 2.4 GHz. It weighs only 17g.
Figure 46: Receiver FSR6B
15.2.5 Selected Microcontroller Unit (MCU)
The MCU used in this project is the KK Multicopter V5.5 (with Atmega168 chip).
Figure 47: KKmulticopter v5.5 control board
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15.2.6 Selected Battery
LiPo (or Lithium Polymer) batteries are rechargeable batteries, normally are composed of
several identical secondary cells in parallel addition to increase the discharge current capability.
They provide high current capacity and discharge rate to weight ratio. They have also great life cycle
degradation rate.
A LiPo battery package have more than 1 cell, voltage of a LiPo cell varies from 7V
(discharged) to about 11.1V (fully charged). The battery or cell capacities are rated in ampere hours
(Ah) or mill ampere hours (mAh). And they are also rated in C which is the maximum discharge rate.
In determining what battery would best suite our needs for this project, we had to take many
factors into account. These included, but were not limited to our total flight time and the total current
draw from our four motors. To have a substantial amount of flight time while keeping the total mass
of the quad rotor to a minimum, we decided on a 3 cell 11.1 volt 4400 mAh battery .To determine
the total flight time you must divide the battery’s power rating by the current draw of the four motors
and multiplying by sixty.
The BLDC motors have a continuous current discharge ranging from 5A to 14.8 A per motor,
so maximum discharge is (14.8 A * 4) = 59.2 A. And the average current drain during the flight is
5.5 A per motor (5.5 A * 4) = 22 A. A 4400 mAh 30C battery was chosen for testing the Quadrotor
and it weighs 895 g.
Figure 48: 3S 30C 4400mah LiPo battery
The battery has maximum discharge of (4.4 Ah * 30) = 132 A, and can run the Quadrotor for
a minimum of (4.4Ah * 60) / 59.2 A = 4.459 minutes (theoretically).
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16. HARDWARE SPECIFICATION
16.1 Mechanical
Hollow square cross section Aluminium Bar
Bar1
Length: 720mm
Beadth: 20mm
Height: 20mm
Thickness: 2mm
Bar2 and 3
Length: 350mm
Breadth: 20mm
Height: 20mm
Thickness: 2mm
Two Square Aluminium mount plate
Length: 205mm
Thickness: 2mm
Four Tubular Plastic landing gear
Length: 300mm
Thickness: 1mm
Diameter: 3cm
Two clockwise and two anti-clckwise propellers with propeller mounts.
Material: Plastic
Dimension: 10*4.5 inches
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16.2 Electrical
Four Brushless outrunner DC motor
RPM: 1800 per volt
Power: 66W
Max Amps: 14.8A
Shaft Diameter: 2mm
Diameter: 25mm
Motor plug: 3mm bullet connector
Weight: 30g
Four Electronic Speed Controllers (ESCs)
Constant current:30A
Burst current: 40A
Weight: 35g
KK Multicopter v5.5 Control board
IC: Atmega168PA
Gyro: Murata piezoelectric gyros
Input voltage: 3.3-5.5V
Signal from receiver: 1520us(4 channels)
Signal to ESC: 1520us(6 Channels)
Weight:15g
FlySky CT6B Transmitter
Channels: 6
Model type: Heli, Airplane ,Glide
RF Power: <=20db
Code type: 2.4Ghz with no interference
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FlySky R6B Reciever
Channels: 6
RF power: <=20db
Frequency: 2.4Ghz
Weight: 15g
Battery
Battery Power rating: 4400mah
No. of cells: 3
Nominal voltage: 11.1V
Continous discharge: 30C
Maximum discharge rate: 132 A
Weight: 895 g
Connectors
Bullet connectors
Wire Harness
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17. DESIGN METHODOLOGY
17.1 Frame Construction
Quadcopter booms were made using hollow square cross section Aluminium bar.
Central hub for placing control board and battery are made using square Aluminium plate.
Aluminium bars and Aluminium plates were drilled to hold them together.
After that, inorder to place the motors on far end of each boom, the booms have been
drilled appropriately. Central hub was drilled in such a way so as to place the control
board in its center.
Additional holes are drilled on the center plate for reducing weight and for passing wires
through it.
Landing gears are made using bendable Aluminum tubes. Holes were drilled on the ends
of tubes at a distance same as that for motor, so that each tube can be fixed below motor
using the same nut and bolt.
Landing gear has been kept in such a way that the propeller should not touch the surface
even if when the quadcopter lands in an inclined way.
Figure 49: Fabrication works done.
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17.2 Soldering electronic components
Soldering has been done on different electronic components for fixing bullet connectors.
Male bullet connectors have been soldered on 3 wires of each motor and female bullet
connectors are soldered to 3 wires of ESCs one end for connecting with motor and male
bullet connectors soldered to 2 wires on other side for connecting it with wire harness,
which will provide current supply.
17.3 Fabrication
Assembly of the frame using nuts and the bolts.
Attaching motor and propeller to the frame using the mount.
Attaching landing gear below each motor using the same nuts and bolts of corresponding
motor.
Positioning of the Flight control Board on the top plate using nylon mounts.
Positioning of battery below lower plate.
Connect the motors and electronic speed control unit to the battery using wire harness and
the control board connection to the Flight control board.
17.4 Setting up the KKmulticontroller
Updating the Firmware
The v.5.5 Blackboard has an Atmega168 chip on board which allows users to tweak and load non
standard firmware. Set IC Fuses & Flash Flashing the Firmware.
Connect the AVRISP Mk2 (or similar) Programmer to the six pin ISP header on the
Kkmulticontroller board.
Connect your Programmer's 6 pin socket to the ISP header on the board. Pin 1 on the ISP header is
usually marked with a small triangle. Then connect the 5V DC power source to the PCB pins.
Figure 50: kk Multicopter usb connector
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Update firmware for Xcopter using kk Multicopter flashing tool.
Figure 51: kkmulticopter flash tool
Checking transmitter channels:
Take off the propellers.
Turn on transmitter and flight controller.
Set throttle to about 1/4. Motors should start.
Move pitch (elevator) stick forward. Back motor should speed up. If not, reverse pitch
(elevator) channel.
Move roll (aileron) stick to the left. Right motor should speed up. If not, reverse roll
(aileron) channel.
Move yaw (rudder) stick to the left. Front and back motor should speed up. If not, reverse
yaw (Rudder) channel.
Transmitter throttle adjustment:
Turn on transmitter and flight controller.
If led does not turn on and stays on, lower your trim.
If still no go, you may need to reverse the throttle channel.
On Tri v1.5 and Quad v4.5 firmware and above, you need to Arm your board by putting
the left stick down and to the right for the LED to come on. If this does not happen, adjust
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your throttle and yaw trim down and to the right on your transmitter. Make sure you do
not have any mixing switches on your Transmitter enabled.
Initial transmitter ATV/servo range settings:
Pitch (elevator): 50%
Roll (aileron): 50%
Yaw (rudder): 100%
ESC throttle range:
Turn yaw pot to zero.
Turn on transmitter.
Throttle stick to full.
Turn on flight controller.
Wait until the ESCs beep twice after the initial beeps. (Plush and SS ESC's)
Throttle stick to off. ESCs beep.
Turn off flight controller.
Restore the yaw pot.
Initial Gyro gain pot value is 50%. Increase until it starts to oscillate rapidly, then back off until it is
stable again. Fast forward flight needs lower gain.
Too low gain is recognized by the multicopter being hard to control and/or always wanting to tip
over.
Checking gyro directions:
Take off the propellers.
Turn on transmitter and flight controller.
Set throttle to about 1/4. Motors should start.
Tilt multicopter forward. Forward motor should speed up. If not, reverse pitch gyro.
Tilt multicopter to the left. Left motor should speed up. If not, reverse roll gyro.
Turn multicopter CW. Front and back motor should speed up. If not, reverse yaw gyro.
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Reversing gyros:
Set roll gain pot to zero.
Turn on flight controller.
LED flashes rapidly 10 times.
Move the stick for the gyro you want to reverse.
LED will blink continually.
Turn off flight controller.
If there is more gyros to be reversed, goto step 2, else set roll gain pot back.
Final check:
Hold the multicopter firmly over our head and slowly advance to about 1/2 throttle. Hold it
steady when you start increasing the throttle, becouse the multicontroller calibrates its gyros when throttle
leaves zero, and then the gyros need to be at rest
17.5 Setting the transmitter
We have used T6config.exe software for setting transmitter for quadcopter.
Figure52:T6config software interface
Selecting the COM port on setting.
End point: For giving the value(0-120) of starting and endpoint of 4 channels.
Reverse: For reversing the stick movement of 4 channels.
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Sub trim: For giving the trim points of all the 4 channels of transmitter.
Mode: For customizing the control stick.
Mode 2 is selected in software for transmitter.
17.6 Binding of ESCs with receiver and transmitter
Individual ESC connected with motor is binded with receiver by placing the bind plug on
battery slot of receiver and placing the servo plug on the desired channel (throttle).
Now, plug the battery to ESC and switch on the transmitter. Wait till the red light on the
receiver stops blinking and gives a constant light.
If receiver give constant red light , then the ESC is binded to the receiver.
Do the same for all other ESCs individually and combined.
17.7 Programming and calibration of ESCs
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17.8 Testing the frame for stability
17.9 Adjusting the gyro for stability by adjusting pitch, roll and yaw gain.
17.10 Performing final flight.
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18. Introduction to the KKmulticontroller
The KKmulticontroller is a flight control board for remote control multicopters with 2,3,4
and 6 rotors. Its purpose is to stablise the aircraft during flight. To do this it takes the signal from the
three gyros on the board (roll, pitch and yaw) and feeds the information into the Integrated Circuit
(Atmega IC). This then processes the information according the the KK software and sends out a
control signal to the Electronic Speed Controllers (ESCs) which are plugged onto the board and also
connected to the motors. Depending upon the signal from the IC the ESCs will either speed up or
slow down the motors (and tilt the rear rotor with a servo in a Tricopter) in order to establish level
flight.
The board also takes a control signal from the Remote Control Receiver (RX) and feeds this
into the IC via the aileron, elevator, throttle and rudder pins on the board. After processing this
information, the IC will then send out a signal to the motors (Via the M1 to M6 pins on the board) to
speed up or slow down to achieve controlled flight (up, down, backwards, forwards, left, right, yaw)
on the command from the RC Pilot sent via his Transmitter (TX). In the case of a Tricopter, one of
the pin connectors (M4) will control a servo to achieve yaw authority.
The v.5.5 has an Atmega168 chip on board and an ISP header which gives users the option to tweak
and upload their own controller code.
Flight Configurations
The KKmulticontroller can be used in several different flight configurations depending upon which
firmware is loaded onto the chip.
These configurations are:
KKOsprey (2 Rotor)
KKTricopter (3 Rotor 1 servo)
KKQuadrocopter (4 Rotor + configuration)
KKXcopter (4 Rotor x configuration)
KKSexycopter (6 Rotor)
KKYcopter (6 Rotor Y configuration)
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Mounting the KKmulticontroller in your multicopter.
The v.5.5 KKmutlicontroller uses Murata piezo gyros that are less sensitive to vibration than
SMD type gyros, but it is still a good idea to mount the board on a vibration dampening material.
The board must also be mounted with the white arrow facing the direction of forward flight.
When connecting your Remote Control Receiver (RX) you must connect the white signal
wire of the channels (CH1, CH2, CH3 and CH4) from your RX corresponding to the aileron,
elevator, throttle and rudder to the inner pins on the board while the red (VCC) wires are connected
to the center pins, and the black (GND) wires are connected to the pins on the outer edge of your
board.
Figure : KK Multicopter V5.5
The pins marked M1 to M6 are connected to the 3 pin BEC plug from your ESCs. They
follow the same convention as the RX pins with the white wires connected to the inner pins, the red
wires to the center pins and the black wires to the outer pins. The ESCs and the connected motors are
plugged onto the pins M1 to M6 in the following order depending on flight rotor configuration.
Note also the direction of rotation for each motor. This is achieved by connecting the three
ESC wires to the motors and swapping two of the wires to achieve rotation in the opposite direction.
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KKXcopter (x Configuration)
If the multicopter tries to twist away, check propeller and motor directions, gyro placement and trim
settings. A slight twist is OK.
If not, try to twist the quad. It should resist your movements. More gyro gain gives more resistance.
If it starts to oscillate, reduce the gain. You should not need to reduce the gain below 40%.
Note: the correct procedure for taking off from the ground is as following:
1: The quad and its propellers need to be motionless.
2: Increase the throttle (collective). Just as the throttle leaves zero, gyro calibration is performed.
3: Remember to close the throttle if you lose control. So that the overall damage will be very less.
NOTES: Do not use bigger propellers than you need. Light propellers gives faster response and more
stability.Try to get it to hover at about midstick (1/3 to 2/3 throttle). Use smaller/bigger propeller,
different motor Kv or more/less Battery cells to achieve that.
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19. Vibration Analysis
Ever since the discovery of resonance by Galileo Galilee in the 17th Century, the study of
vibrations of mechanics has become a vital part of the design of any mechanical system. Because
mechanical systems tend to have natural modes, when a certain force is applied any of the natural modes
can be excited which in turn may lead to catastrophic failure of the system. This in turn leads to the
importance of studying the resonance frequency of the quad rotor. The resonance frequencies of a system
are the frequencies at which the system will be ―excited‖; therefore, it is imperative to determine the
correct resonant frequencies of the quad rotor in order to ensure that the natural modes of the system will
not be disturbed. To do these we have determined the natural frequencies of the propellers, which we
then relate to the resonance frequencies of the quad rotor to ensure the stability of the system.
Analysis and Results
To determine the natural frequencies of the quad rotor the following Equation for the Strouhal
number was used:
𝑆𝑡 = (𝑓∗𝐿)/𝑣
Where St is the Strouhal number, f is the vortex shedding frequency of the propeller, and v is the
velocity of the flow past the propeller. The Strouhal number is an experimentally determined quantity
derived in wind tunnel testing and a quantity of 0.2 is acceptable in our project. The velocity of the flow,
v, is determined analytical by multiplying the angular velocity of the propeller in RPM‟s with the radius
of the propeller. The characteristic length, L, is determined analytically as well by determining the
thickness of the propeller as well as the chord length multiplied by the sine of the angle alpha, which is
the angle of attack. The larger quantity is then substituted for the characteristic length. As a result, we
were able to determine the vortex shedding frequency of the propeller. The following are values for the
two bladed experimentally tested propellers.
Table2: Empirical data for 2 blade propellers.
No. of Blades Length(m) ½ Radius(m) Radius(m)
2 0.018 0.127 0.254
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Using the values presented above the vortex shedding frequencies, f, were determined for values
of RPM ranging from 0 to 19980rpm, which is the maximum angular velocity of the propellers. The
following graph represents the calculated values of vortex shedding frequency as a function of ω for the
two bladed propeller.
Figure 53: Thrust of lifting force vs Voltage drop of battery
Natural frequency of vibration of cantilever Aluminium spar is given by the equation:
Wn=(3EI/(L3*rho*V))1/2
As presented in the graph, there is a strong linear correlation between the increase in vortex
shedding frequency and the increase in omega. The values for the vortex shedding frequency are an
average for each propeller as the speed of the flow past the propeller was calculated at one-half the total
radius of the propeller.
These results are significant when compared to the analysis of determining what the natural
resonance frequency of the structure is completed. To determine the natural resonance frequency of the
structure we assumed a rigid body with the carbon fiber spars representing beams with one free end and
one fixed end. From this assumption, we determined what the effects on the spar will be when there was
a force applied (the force of the propeller).
Obtained natural frequency for cantilever Aluminium spar is 181.84 rad/s or 28.95Hz.
The vortex shedding frequency of the used propeller is 423Hz.
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So by comparing the obtained values, at no time does the vortex shedding frequency of propellers excites
in any of the modes. This leads us to conclude that barring any resonance within the electronics our quad
rotor is structurally sound.
20. Vibration Isolation
The performance of an isolation system is determined by the transmissibility of the system—the ratio
of the energy going into the system to the energy coming from the system. This can be expressed in
terms of acceleration, force or vibration amplitude. Transmissibility (T) is equal to
Where: T= Transmissibility
Aout= Energy out of system (transmitted force)
Ain= Energy into system (Disturbing force)
fd= Driving frequency
fn= Natural frequency
Figure54 : T
At very low frequencies (fd/fn << 1), the input vibration virtually equals output (the
transmissibility is equal to 1), and input displacement essentially equals that of output.
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If the driving frequency equals the natural frequency (fd/fn = 1), the system operates at
resonance. If damping is ignored in the equation for transmissibility that was given earlier, a system
that is operating at resonance will have a transmissibility approaching infinity.
As damping increases, the transmissibility at resonance decreases. Below figure shows the
relationship between peak natural frequency at resonance and loss factor. Of course, all real world
systems have some level of inherent damping, but this demonstrates the important role that damping
can play in vibration isolation. When a vibration isolation mount with very little damping is used at
or near resonance, the energy amplification can create many problems, ranging from a simple
increase in noise levels to catastrophic damage to mechanical equipment.
Figure 55: relationship between peak natural frequency at resonance and loss factor.
When the frequency ratio equals the square root of two (fd/fn =√2), transmissibility will once
again drop to 1. This is known as the crossover frequency, and the area below this frequency is
known as the amplification region. Above this frequency lies the isolation region, where
transmissibility is less than 1. As a goal, the isolator designer tries to design a mounting system that
puts the primary operating frequencies of the system in the isolation region. Many systems must
operate at a number of primary frequencies or must frequently go through a startup or slowdown as
part of the operation cycle. For these systems, damping in the mount becomes increasingly important
when it must function at or near resonance.
As frequency continues to increase above the crossover frequency, the level of isolation, or
the isolation efficiency, increases. Below figure shows this relationship. Designers must know the
isolation efficiency of the mounting system when transferred energy must be below a specified level,
in devices such as CD-ROM or hard disk drives.
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Figure 56: Isolation efficiency vs Crossover frequency ratio
20.1 General cases
In Vibration Isolation, two cases arise viz.
1. In the First situation we have
The foundation of a machine is protected against large unbalanced forces or
impulsive forces.
Modeling the system as a single d.o.f. system.
The force is transmitted to the foundation through spring and damper.
The force transmitted to the base (Ft) is given by
Ft(t) = kx(t) + cx·(t)
To achieve isolation, the force transmitted to the foundation should be less than excitation force.
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In the second type, the system is protected against the motion of its foundation (as in the case of
protection of a delicate instrument from the motion of its container).
Modeling the delicate instrument as a single d.o.f. system
The force transmitted to the instrument (mass m) is given by:
Ft(t) = m x’’(t) + k[x(t)-y(t)] + c[x'(t)-y'(t)]
where (x-y) and (x’-y’) denote the relative displacement and relative velocity of the spring and
damper respectively.
Figure 58
20.2 Types of Vibration Isolation
1. Passive isolation
"Passive vibration isolation" refers to vibration isolation or mitigation of vibrations by passive
techniques such as rubber pads or mechanical springs, as opposed to "active vibration isolation" or
"electronic force cancellation" employing electric power, sensors, actuators, and control systems.
Figure 57: Single Degree of Freedom
system
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Passive vibration isolation is a vast subject, since there are many types of passive vibration isolators
used for many different applications. A few of these applications are for industrial equipment such as
pumps, motors, HVAC systems, or washing machines; isolation of civil engineering structures from
earthquakes (base isolation), sensitive laboratory equipment, valuable statuary, and high-end audio.
How Passive Isolation Works
A passive isolation system in general contains mass, spring, and damping elements and moves as a
harmonic oscillator. The mass and spring stiffness dictate a natural frequency of the system.
Damping causes energy dissipation and has a secondary effect on natural frequency.
Figure 59
Every object on a flexible support has a fundamental natural frequency. When vibration is applied,
energy is transferred most efficiently at the natural frequency, somewhat efficiently below the natural
frequency, and with increasing inefficiency (decreasing efficiency) above the natural frequency. This
can be seen in the transmissibility curve, which is a plot of transmissibility vs. frequency.
Here is an example of a transmissibility curve. Transmissibility is the ratio of vibration of the
isolated surface to that of the source. Vibrations are never completely eliminated, but they can be
greatly reduced. The curve below shows the typical performance of a passive, negative-stiffness
isolation system with a natural frequency of 0.5 Hz. The general shape of the curve is typical for
passive systems. Below the natural frequency, transmissibility hovers near 1. A value of 1 means that
vibration is going through the system without being amplified or reduced. At the resonant frequency,
energy is transmitted efficiently, and the incoming vibration is amplified. Damping in the system
limits the level of amplification. Above the resonant frequency, little energy can be transmitted, and
the curve rolls off to a low value.
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2. Active Vibration Isolation
In active vibration isolation system among the spring there is feedback circuit which consists of a
piezoelectric accelerometer, an analog control circuit, and an electromagnetic transducer. The spring
supports the weight of the table top and the device which is mounted on the table. The motion of the
table top is detected by a highly sensitive piezoelectric accelerometer consisting of a mass resting on
a piezoelectric disc and covered by housing. The acceleration signal is processed by analog control
circuit and amplifier. Then it feeds the electromagnetic actuator, which is designed analogously to
loudspeaker. The magnet of actuator is located on a movable table, and the electrical coil is
connected with platform. As a result of such feedback system we can achieve considerably stronger
suppression of vibrations as compared to ordinary damping. Animation shows one of variants of
active vibration isolation system with two accelerometers and electromagnetic transducers. The track
in the bottom part of animation shows the record of the noise displacement of a vibrating platform.
The top track is the residual displacements of the stabilized table enlarged 100 times. We can see in
animation that such a system allows considerable reduction of amplitude of the table oscillation to be
achieved, especially in high-frequency region.
Figure 60: Transmissibility vs Frequency
The figure on the right shows the difference in transmissibility of passive and active damping
systems simulated with the aid of computer. The signal of accelerometer was integrated, so the
feedback signal applied to electromagnetic actuator was proportional to velocity of the table top. Red
curve corresponds to the case when feedback was switched off. We can see the resonance pick at
frequency of about 0.6 Hz. Green curve shows the case when weak feedback was switched on. This
weak feedback removed the resonance pick, while the transmissibility at low and high frequencies
was about the same. And, finally, blue curve shows the influence of the strong feedback signal. We
can see that residual vibrations are considerably suppressed from low frequencies up to about 10 Hz.
Feedback coefficients for green and blue curves are related as 1 to 15. Maximal advantage of active
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vibration isolation system can be achieved in the middle frequency region, near resonance, which is
very important for most of practical applications.
Figure 61
Passive vs. Active Isolation
Regarding the equations for the transmission it can be seen that passive isolation always exhibits
amplification within the resonance and the isolation for higher frequencies decreases because of the
viscous damping. The plot below shows the transmission calculated for passive and active isolation.
The eigenfrequency has been set to 5Hz which is a very common value for passive isolation systems.
Unfortunately the excitation from the building often occurs at the same frequency range. For this
reason the remaining amplitude on top of the passive isolation system is higher than the amplitude on
the floor of the building.
Figure 62: Transmission vs frequency
Another advantage of an active isolation system compared to a passive stage is the short settling
time. The red curve of the plot below demonstrates the importance of a low eigenfrequency for
passive systems since the isolation effect takes place for frequencies above the resonance. The low
eigenfrequency combined with low damping leads to a long time constant. The passive system needs
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a long time to come to rest again. In the case of the active system the vibration decays much faster
because the active system reacts with its actuators. The actuators are generating forces which
counteract the movement of the isolated mass.
21. Vibration Isolation of the Quad rotor design
Vibration isolation is an important part of the design because is the natural frequency of vibration of
the frame coincides with the vortex shedding frequency of the propellers; resonance can occur and
lead to severe increase in the amplitude of the vibration.
The components creating vibrations is the rotating propellers, so the vibration generated as to be
isolated from reaching the board. The microcontroller board used for the design must be free of the
vibration for the efficient performance.
Passive Isolation technique was implemented for our design
So, the following components were used to obtain the vibration isolation viz.
1. Nylon screws (Figure 63)
The controller board was mounted on the nylon screws for efficient vibration isolation.
2. Plastic Pads (Figure 64)
The plastic pads were used on the frame from the end of the motor to the place where the
board was placed.
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22. Catia Drawings of Frame Components
The components that were drawn on CATIA were
Main Frame( Spar)
Two cross frames
Top flat plate
Bottom flat plate
Motors
Propellers
Steps involved in the Drawing
The above components were created in the part modelling environment. The commonly used
commands were PAD (to extrude the drawing).
Once, all the individual components were created, the each of the components were
transferred to the Assembly environment. Each of the components was first imported in the
Assembly Environment.
An assembly is a document (also called as a CAT product) that stores a collection of
components (parts or the other assemblies). An assembly uses .CATPRODUCT extension. The
components used in the assembly can be pre-existing components or components created
within the assembly.
The components were assembled in the assembly environment.
The motion simulation was performed in the DMU (Digital Mock up Environment)
Kinematics
Once, all this was performed, and then the Drafting Environment was used to create
dimensions and views of all the components and the assembly as a whole.
Drafting workbench generates 2D views from the 3D geometry
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Schematic Model of the Design process (Figure 65)
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1. Main Frame (Figure 66)
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2. Cross Frame (Figure 67)
3. Top Plate (Figure 68)
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4. Bottom Plate (Figure 69)
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5. Propeller (Figure 70)
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6. Motor (Figure 71)
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7.QUAD COPTER FULL VIEW (Figure 72)
Front View
Diagonal View
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The Upper plate shown has small holes at the center that can be used for mounting the control
board and additional holes has been put to allow the passing of the wires and weight
reduction.
The Holes at the end of each frame can be used to mount the motor and the propeller.
The bottom plate has holes to attach the landing gear and another mounting plate would be
attached to it to carry the battery.
Side View
Isometric View
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23. RESULTS
This section includes the results of structures, aerodynamics, propulsion, control and Flight
testing parts respectively.
STRUCTURES
The structures part of the project has been accomplished. The set goals has been met as we
have designed and fabricated the frame of the quadcopter along with the motors and electronics of
the propulsion and controls teams. The structural analysis of the frame has been done using ANSYS
and from the results we have seen that the quadcopter structure is strong and reliable enough to
withstand the forces and moments imposed on the quadcopter.
PROPULSION
The Propulsion team has accomplished all objectives set to develop a propulsion system
satisfying the requirements of this project and to implement it on the actual model. The team along
with the control team has arranged all the equipments like motor, propeller, ESC , battery etc
required for the propulsion system of our project.
CONTROLS
The control team arranged all the equipments which needed to control the quadcopter during
take-off, flying and landing. For this RC, ESCs, motors and a control board were purchased and
installed on the frame .The control team then programmed the control board and the ESCs with the
help of online softwares available and binded all the ESCs so they can coordinate with one another.
FLIGHT TESTING
PRE-FLIGHT TESTING
Before the quadrotor could be tested in free flight, it had to be determined that it would not
respond in a way which would damage itself. First, all of the sensors were connected to the
quadcopter, but not actually mounted on it. This allowed manipulation of the sensors while
allowing the motors to run, but prevented the quadrotor from actually moving. This was a
qualitative test simply to ensure that the motors were responding quickly to variations in
attitude and altitude.
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FLIGHT ATTEMPTS
The quadrotor is still going through flight testing which includes tuning of the gyro and to
program various electronic components to get the most accurate data out of the them. The
basic problem is that all the four rotors are not rotating simultaneously and this is causing the
lift production on one side of the quadcopter only.
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24. Future Works
Improvement of Strength to weight ratio.
Use of composites instead of Aluminium for making frame (central hub and 4 booms) and
landing gear will help us in increasing the strength to weight ratio.
Composites are lighter and stronger than Aluminium.
Quadrotor made of composites will be having less weight as compared to same quadrotor
made with Aluminium. It is because of the reason that composites have less density than
Aluminium.
Quadrotor made with composites will be giving least deflection for given loads acting.
Payload Capacity.
Use of composites
Use of more powerful battery
Use of higher RPM motors and better ESCs.
Removing unwanted parts of frame.
Additional Integration of Electronic equipments.
We would need sensors including compass, GPS, and a battery monitor.
We would also need payload components including a camera and a telemetry system to send
imagery back to the liftoff site.
Autonomous Control System.
We would need a control mechanism that would allow flight beyond the line of sight.
Two approaches that can be done for control beyond the line of sight.
Use of camera and video to allow us to view the flight path from the Quadcopter point of
view while guiding it with an RC controller.
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Use of onboard GPS and guidance and a waypoint system to send commands to the
Quadcopter via the telemetry link which the Quadcopter would execute autonomously.
Improved Range and Endurance.
By reducing weight, the maximum discharge rate required for battery will reduce as the
motor requires less current. Hence, endurance of quadcopter will increase.
Increased power of motor for better altitude.
Increased power rating of battery for better endurance
Use of higher bandwidth transmitter and receiver for improving range.
Design Improvement
Use of streamlined frame.This can be achieved by better aerodynamically designed booms
and central hub of the frame.
Use of protection for propellers from hitting aand throwing away as shown in figure.
Figure 73
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25. CONCLUSIONS AND DISCUSSIONS
Our entire project was aimed at the design of the Vertical Takeoff UAV. Selected
configuration for the project was the Quad copter design. This design was initiated with the
preliminary calculations to obtain the configurations of the various electronic components. The
primary component that decides the time of flight is the battery. The battery chosen was suitable as
per the calculations have 40C burst current able to supply total current of 132 A.
The other electronic components like the motors, electronic speed control units were selected
as per the requirements. The main part of this configuration is the KK multicopter controller board
which forms the heart of the design was integrated to ensure stability to the design. The control board
has intrinsic capability to maintain the pitch, yaw and roll disturbances, with the help of inbuilt
Accelerometers and Gyros.
The design process began with the attachment of the various structural frame components
like the main spar, two cross spars, main top plate, and bottom plate. Once through with this, main
focus was directed towards the integration and the calibration of all the electronic components, the
main attention being directed towards the electronic speed control units and the multi controller
board.
A crucial deficiency was that, the team members did not have experience working from the
electronics point of view. Howsoever, a lot of time was dedicated to the study of the working of the
electronic components and the way of calibrating each of them.
The main hurdles in the design as per the timeline are as follows
1. During the initial phase of the fabrication part, problem arose regarding the transmission of
signal from the transmitter to the electronic speed control units and to the motors. This
problem was resolved through the Binding process that bound the transmitter to the receiver
and thereafter the signals were effectively getting transmitted.
2. The main problems came into the picture once the controller board was integrated onto the
design. Initially the controller board was not transferring the signal from the transmitter to the
electronic speed control units. This problem was then resolved by configuring the board using
the KK multicopter flash tool. The adequate X copter firmware was renewed on the board
and it started responding.
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3. The problem that persisted on for a longer time was that all the four motors were not running
in unison. Though they start together, but, as the throttle is increased for 0 to 50% some of
the motors stops. Since the motors are not running in unison, hence lifting problem persists.
This problem was tackled in the following ways ( though not fully resolved)
I) First of all, it was checked whether all the electronic speed control units were
not properly responding to the commands given by the transmitter. Since, this
problem arose; hence it was decided to program the entire ESC’s one by one
each. This process was little time consuming. In spite of all this, still the
problem persisted.
II) Another problem that was anticipated was that the propellers may not be of the
adequate size or may not have properly matched with the motors. The
propellers used for our configuration was the 10*4.7. However, the suitable
would be 8x4 / 7x3. But a definitive problem could not be recovered from the
testing. The motors of 1600 rpm/v were actually decided during the initial
calculations. But, there was some problem with the availability of the motors.
The vendor supplied us with the 1800 rpm/v motors. Some problem may have
occurred because of this problem.
III) A yet another problem that was concluded during the testing was that the
bottom plate may have added on some extra weight. This problem was
resolved by removing the bottom plate. This actually showed positive signs of
lifting up. Actually the quad rotor started lifting up a bit from the ground.
Actually during the initial design phase, it was decided to integrate the camera and the Global
positioning system, but since, the problems associated with the quad rotor took a long time to rectify
and moreover the amount expected exceeded, so that integration idea was dropped.
But, in the future, more of the improvements as listed in the Future prospects could be
incorporated in the design.
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APPENDIX
MATLAB Programs
Thrust Plot
clc
clear all
for v = 11.1 : -0.001 : 7
T = 4 * (10^-12) * 1.225 * 3.14 * 25 * (4.7*4.7) * (1800^2) * (v*v);
ha = gca;
set(ha,'xdir','reverse');
plot (v,T,'--b');
hold on
end
ylabel('Thrust or Lifting force , kg');
xlabel('Voltage drop range of battery , Volts(V)');
title('Thrust-Voltage Curve');
grid
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Induced Velocity curve
clc
clear all
for v = 11.1 : -0.001 : 7
T = 4 * (10^-12) * 1.225 * 3.14 * 25 * (4.7*4.7) * (1800^2) * (v*v);
V = (T / 0.124) ^ 0.5;
hold on
subplot(2,1,1);
plot (V,T,'--r');
ha = gca;
set(ha,'xdir','reverse');
hold on
subplot(2,1,2);
plot (v,T,'--b');
ha = gca;
set(ha,'xdir','reverse');
end
subplot(2,1,1);
ylabel('Vel across rotor disk , m/s');
hold on
xlabel('Thrust or Force , kg');
title('Velocity-Thrust Curve');
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grid
subplot(2,1,2);
ylabel('Thrust or Lifting force , kg');
hold on
xlabel('Voltage drop range of battery , Volts(V)');
title('Thrust-Voltage Curve');
grid
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Slipstream velocity
clc
clear all
for v = 11.1 : -0.001 : 7
T = 4 * (10^-12) * 1.225 * 3.14 * 25 * (4.7*4.7) * (1800^2) * (v*v);
V = (T / 0.124) ^ 0.5;
w = 2 * V;
hold on
subplot(2,1,1);
plot (w,T,'--r');
ha = gca;
set(ha,'xdir','reverse');
hold on
subplot(2,1,2);
plot (v,T,'--b');
ha = gca;
set(ha,'xdir','reverse');
end
subplot(2,1,1);
ylabel('Slipstream velocity , m/s');
hold on
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xlabel('Thrust or Force , kg');
title('Slipstream-Thrust Curve');
grid
subplot(2,1,2);
ylabel('Thrust or Lifting force , kg');
hold on
xlabel('Voltage drop range of battery , Volts(V)');
title('Thrust-Voltage Curve');
grid
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Disk loading
clc
clear all
T = 26.9794; % Thrust in Newtons
for r = 0.0762 : 0.0001 : 0.1778
A = 3.14 * r * r; % Disk area
Dsk_load = T / A; % Disk Loading
plot (r,Dsk_load,'--m');
hold on
end
ylabel('Disk Loading , N/m2');
xlabel('Propeller Radius , m');
title('Disk loading Curve');
grid
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Angular Velocity
clc
clear all
for v = 11.1 : -0.001 : 7
Omega = (1800 * v) / 60;
ha = gca;
set(ha,'xdir','reverse');
plot (v,Omega,'--b');
hold on
end
ylabel('Angular Velocity , rad/sec');
xlabel('Voltage drop range of battery , Volts(V)');
title('AngularVel-Voltage Curve');
grid
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Structural Plots
Deflection curve
clc
clear all
for l = 0.6 : 0.0001 : 0.72
delta_Al = (26.9794 * l * l * l) / (3 * (70 * (10^9)) * (1.3 * (10^-8)));
% Deflection of Aluminium
delta_Ba = (26.9794 * l * l * l) / (3 * (6 * (10^9)) * (1.3 * (10^-8)));
% Deflection of Balsa Wood
delta_Bir = (26.9794 * l * l * l) / (3 * (16.59 * (10^9)) * (1.3 * (10^-8)));
% Deflection of Birch Wood
delta_PVC = (26.9794 * l * l * l) / (3 * (4.14 * (10^9)) * (1.3 * (10^-8)));
% Deflection of PVC
delta_Carfib = (26.9794 * l * l * l) / (3 * (631 * (10^9)) * (1.3 * (10^-8)));
% Deflection of Carbon Fibre
delta_Ny = (26.9794 * l * l * l) / (3 * (2.61 * (10^9)) * (1.3 * (10^-8)));
% Deflection of Nylon
plot(l,delta_Al,'c-',l,delta_Ba,'m-',l,delta_Bir,'y-',l,delta_PVC,'r--',l,delta_Carfib,'g:',l,delta_Ny,'b--');
hold on
end
legend('Aluminium','Balsa Wood','Birch wood','PVC','Carbon fibre','Nylon');
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ylabel('Deflection , m');
xlabel('Length of the beam , m');
title('Deflection Curve');
grid
Vortex shedding frequency program
clc
clear all
for v = 7 : 0.001 : 11.1
f = (0.2 * 0.127 * 1800 * v) / 0.018;
plot (v,f,'--b');
hold on
end
ylabel('Thrust or Lifting force , Hz');
xlabel('Voltage drop range of battery , Volts(V)');
title('Vortex Shedding Frequency Curve');
grid
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CATIA
CATIA is a robust application that enables you to create rich and complex designs. CATIA is
mechanical design software. It is a feature based (made up of individual elements called as Features),
parametric (Driving Dimensions are used while creating a feature. These include dimensions that are
associated with the Sketched geometry as well as with the feature itself) solid modelling (A solid
model includes all the necessary wireframe and surface geometry needed to describe the edges and
faces of the model) design tool that takes the advantage of the easy to learn Windows graphical user
interface. You can create fully associative (A CATIA 3D model is fully associative with the
drawings and parts that reference it) 3D models, with or without the constraints, while using
Automatic or user defined relations to capture the design intent.
CATIA Applications in the Industries.
The Boeing Company used CATIA V3 to develop its 777 airliner, and used CATIA V5 for the 787
series aircraft. They have employed the full range of Dassault Systems' 3D PLM products — CATIA,
DELMIA, and ENOVIA LCA — supplemented by Boeing developed applications.
The development of the Indian Light Combat Aircraft has been using CATIA V5.
Chinese Xian JH-7A is the first aircraft developed by CATIA V5, when the design was completed on
September 26, 2000.
European aerospace giant Airbus has been using CATIA since 2001.
Canadian aircraft maker Bombardier Aerospace has done all of its aircraft design on CATIA.
The Brazilian aircraft company, EMBRAER, use Catia V4 and V5 to build all airplanes.
Vought Aircraft Industries use CATIA V4 and V5 to produce its parts.
The Anglo/Italian Helicopter Company, AgustaWestland, use CATIA V4 and V5 to design their full
range of aircraft.
The Eurofighter Typhoon has been designed using both CATIA V4 and V5.
The main supplier of helicopters to the U.S Military forces, Sikorsky Aircraft Corp., uses CATIA as
well.
Bell Helicopter, the creator of the Bell Boeing V-22 Osprey, has used CATIA V4, V5, and now V6.
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Catia stands for Computer Aided Three dimensional Interactive Application. The version of
CATIA used for our Drawings is V5.
Introduction to Ansys Workbench
ANSYS Workbench combines the strength of our core product solvers with the project
management tools necessary to manage the project workflow. In ANSYS Workbench, analyses are
built as systems, which can be combined into a project. The project is driven by a schematic
workflow that manages the connections between the systems. From the schematic, you can interact
with applications that are native to ANSYS Workbench (called workspaces) and that display within
the ANSYS Workbench interface and you can launch applications that are data-integrated with
ANSYS Workbench, meaning the interface remains separate, but the data from the application
communicates with the native ANSYS Workbench data.
Native workspaces include Project Schematic, Engineering Data, and Design Exploration
(Parameters and Design Points). Data-integrated applications include the Mechanical APDL
application (formerly ANSYS), ANSYS FLUENT, ANSYS CFX, the Mechanical application
(formerly Simulation), etc.
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26. REFERENCES
"BYU Quad Rotor Senior Project.". Brigham Young University
http://www.et.byu.edu/groups/quad08buldog/structure/basic_design.php.
UAV Laboratory. Clemson Univerisity ECE Department
http://www.ece.clemson.edu/crb/research/uav/index.htm.
http://en.wikipedia.org
http://draganfly.com
http://mikrokopter.de
http://microcontroller.com
http://hobbycity.com
http://youtube.com
Helicopter History.
http://www.helis.com/timeline/sikorsky.php
Oemichen. http://www.aviastar.org/helicopters_eng/oemichen.php